Dormant Season Evapotranspiration in Alfalfa

Weekly values of maximum temperature, minimum temperature, and solar radiation were examined for their effect upon weekly dormant season evapotranspiration (ETdorm) in perennial alfalfa. In addition, the total amount of ETdorm was evaluated for its contribution to first harvest yield. Results from 9 years of data indicate that highly significant (p equals 0. 01) simple linear correlations are frequently not significantly different among years. A linear production constant of 2. 02 multiplied by 10** minus **3 kg. m** minus **2. mm** minus **1 shows that the 5 months of ETdorm contribute an average of 20% of the yield of the first spring harvest.